1. Field of the Invention
This invention relates to an energy attenuating apparatus for use with a seat that can absorb energy applied to the seat and a seat occupant during a sudden deceleration such as may occur during a crash of an aircraft. It also relates to a seat equipped with such an energy attenuating apparatus.
2. Description of the Related Art
Seats of aircraft, and particularly military aircraft, are frequently equipped with devices generally referred to as energy attenuating apparatuses for absorbing energy generated during a crash or other sudden deceleration so as to reduce the forces applied to a seat occupant and thereby protect the seat occupant against injury. A number of energy attenuating apparatuses work on the principle of plastic deformation of an elongated member. One type of energy attenuating apparatus that has found significant use has an elongated wire, which passes along a nonlinear path between a plurality of rollers. When a force above a certain level acts on the energy attenuating apparatus, the rollers and the wire undergo translation with respect to each other, producing plastic deformation of the wire over a portion of its length as the region of the wire engaging the rollers moves down the length of the wire to dissipate kinetic energy of the seat and the seat occupant. The distance by which the rollers and the wire translate with respect to each other during actuation of the energy attenuating apparatus is referred to as the stroking distance of the energy attenuating apparatus. The stroke depends upon the energy to be dissipated by the energy attenuating apparatus during a crash and the resistance of the wire to deformation.
Existing energy attenuating apparatuses of the type described above employ a constant diameter wire that provides a constant resistance to translation with respect to the rollers over its length. The wire diameter is selected so that the energy attenuating apparatus can provide suitable energy attenuation during a crash for a seat occupant in the 50th weight percentile. While a seat occupant with a weight near the 50th weight percentile can be adequately protected, a light or heavy occupant may not receive sufficient protection. A light seat occupant may suffer dangerously high loads and very little seat stroking, while a heavy seat occupant may experience very light loads and very long seat stroking. Because of the light loads, the heavy seat occupant may require a greater stroking distance than is available in order for the energy attenuating apparatus to dissipate all of the crash energy. Therefore, a seat with a heavy occupant may bottom out before all the energy is attenuated, resulting in very high loads and energy being transmitted to the seat occupant rather than being dissipated by the energy attenuating apparatus.
The present invention provides an energy attenuating apparatus for a seat that has a varying resistance to deformation over its stroke to enable the energy attenuating apparatus to provide adequate protection to seat occupants over a wide range of weights.
The present invention also provides a seat arrangement employing such an energy attenuating apparatus.
According to one aspect of the present invention, an energy attenuating apparatus for use with a seat includes an elongated attenuator having a resistance to bending which varies along its length, and a bending mechanism defining a nonlinear path receiving the attenuator. Relative movement of the attenuator and the bending mechanism in a lengthwise direction of the attenuator produces bending of the attenuator. Due to the varying bending resistance of the attenuator along its length, when the apparatus is installed on a seat, the apparatus can effectively provide energy attenuation for seat occupants over a wide range of body weights. Namely, it can prevent excessive forces from being applied to a relatively lightweight seat occupant, and it can prevent the seat from bottoming out when used by a relatively heavy seat occupant.
The energy attenuating apparatus may include a housing having first and second portions capable of telescopic movement with respect to each other. The attenuator may be disposed in the housing with first and second ends of the attenuator secured to the first portion, and the bending mechanism may be disposed inside the housing and secured to the second portion. The housing enable the energy attenuating apparatus to be easily installed on a seat or other structure with respect to which the apparatus is to perform energy attenuation.
According to another aspect of the invention, a seat arrangement includes a seat back for supporting a back of a seat occupant, a seat bottom secured to the seat back for supporting buttocks of the seat occupant, a guide engaging the seat back for guiding the seat back along a path, and an energy attenuating apparatus for attenuating energy as the seat back moves with respect to the guide along the path. The energy attenuating apparatus includes an elongated attenuator immobilized with respect to one of the seat back and the guide, and a bending mechanism immobilized with respect to the other of the seat back and the guide and defining a nonlinear path receiving the attenuator. In a preferred embodiment, the attenuator has a resistance to bending which varies along its length.
An energy attenuating apparatus according to the present invention is particularly suitable for use with aircraft seats, but it can be used with seats of any type of vehicle, such as land vehicles or high-speed marine vehicles. It can also be used to attenuate energy in conjunction with devices other than seats, such as parachutes, mountain climbing apparatus and vehicle bumpers.
In a preferred embodiment, an energy attenuating apparatus according to the present invention is installed on a seat so as to resist forces acting on the seat primarily in a direction parallel to the height direction of the seat, but it can also be used to resist forces acting on a seat in a fore-and-aft direction, in a lateral direction, or in a combination of different directions.
The resistance to bending of the attenuator can be varied along its length in a variety of manners, such as by varying the transverse cross-sectional area or the material properties of the attenuator. The resistance to bending can be selected so that the energy attenuating apparatus exerts predetermined forces within a permissible range to a wide range of the population during a crash while maintaining the stroking distance of a seat at a level so that bottoming out does not occur. For example, the attenuator can be selected to provide adequate protection during a crash to seat occupants ranging in weight from the 3rd percentile of females to the 98th percentile of males, with the maximum stroking distance remaining below about 14 inches.